This invention relates to apparatus for protectively housing a wide variety of electrical devices used in either CATV or other communication systems, and in particular, to a shielded housing for enclosing a CATV passive device such as a directional tap or the like.
In community antenna television systems (CATV), communication signals are typically transmitted to subscriber locations by means of coaxial distribution cables. Each cable has a grounded metal sheath that shields a signal carrying center conductor from unwanted interference. A number of passive devices referred to as taps are positioned along the distribution lines which enable one or more drop lines to be connected to the distribution line by which communication signals are diverted to various subscriber locations. These passive devices are generally contained in protective housings that are specifically adapted to electrically shield and physically protect the enclosed circuit elements from radio frequency interference and the surrounding ambient.
Television cable systems may be installed either above ground or below ground. In an above ground installation, protective housings containing these passive devices are suspended between poles upon support wires. The television distribution cable is connected to each housing in a straight through configuration by means of axially aligned access ports provided in the opposing side walls of each housing. This straight through cable arrangement minimizes cable bending and facilitates the routing of the cable along existing telephone line systems Housings used in the in ground installations, on the other hand, are generally mounted upon pedestals. In this arrangement, the distribution cable is run into and out of the housing through parallelly aligned access ports contained in the front wall of the housing
As described by Norberg et al. in U.S. Pat. No. 4,025,150 it is common in the industry to provide two sets of access ports in each protective housing so that it can be adapted for use in either an above ground or an in ground installation. Plugs are placed in the unused ports to prevent moisture and dirt from passing into the housing As further disclosed by Norberg et al., both the base and cover sections of the protective housing have heretofore been die cast of aluminum or some other conductive metal. The heavy metal castings provide good electrical shielding for the housed electrical components, however, the castings, because of the nature of the fabrication process, tend to be porous. As a result, moisture is able to penetrate the walls of the housing and attack the enclosed electrical components. In the case of an aluminum casting, the metal deteriorates rapidly when exposed to weather in an outdoor or free environment. The casing generally must be chemically treated and/or painted to render the housing sections weather proof. This, of course, is expensive and considerably increases the unit cost of the housings.